Electrophotographic recording material with a photoconductive carbazole compound

ABSTRACT

Recording process comprising exposing to imagewise modulated electromagnetic radiation a photoconductive insulating recording element comprising an organic photoconductive compound corresponding to one of the following general formulae:   wherein: EACH OF Z1 and Z2 (the same or different) represents the necessary atoms to close an adjacent ring or ring system including such ring or ring system in substituted form, Ar represents a bivalent aromatic group, EACH OF R1 and R2 (the same or different) represents hydrogen, an aliphatic group including a cycloaliphatic group or said groups in substituted form, or an aryl group, OR R1 and R2 together represent the necessary atoms to close a nitrogen-containing ring including such a ring in substituted state.   wherein: Z1 and Z2 have the same significance as described in general formula I, A represents an alkylene group or an alkylene chain interrupted by a phenylene group, and Ar represents a bivalent aromatic group.

United States Patent [191 J anssens et al.

[4 1 Oct. 14, 1975 ELECTROPHOTOGRAPHIC RECORDING MATERIAL WITH A PHOTOCONDUCTIVE CARBAZOLE COMPOUND [75] Inventors: Wilhelmus Janssens, Aarschot; Jozef Aime Dierckx, Mechelen; Hendrik Hubert, Wijnegem, all of Belgium [73] Assignee: Agfa-Gevaert, a naamloze vennootschap, Mortsel, Belgium 22 Filed: Sept. 21, 1973 21 Appl. No.: 399,503

Primary ExaminerNorman G. Torchin Assistant Examiner-John L. Goodrow Attorney, Agent, or Firm-William J. Daniel [57] ABSTRACT Recording process comprising exposing to imagewise modulated electromagnetic radiation a photoconductive insulating recording element comprising an organic photoconductive compound corresponding to one of the following general formulae:

each of Z and Z (the same or different) represents the necessary atoms to close an adjacent ring or ring system including such ring or ring system in substituted form,

Ar represents a bivalent aromatic group,

each of R and R (the same or different) represents hydrogen, an aliphatic group including a cycloaliphatic group or said groups in substituted form, or an aryl group,

or R and R together represent the necessary atoms to close a nitrogen-containing ring including such a ring in substituted state.

Z and Z have the same significance as described in general formula I,

A represents an alkylene group or an alkylene chain interrupted by a phenylene group, and

Ar represents a bivalent aromatic group.

8 Claims, No Drawings ELECTROPHOTOGRAPHIC RECO Ar represents a bivalent aromatic group e.g. a pheny- MATERIAL WITH A PHOTOCONDUCTIVE lane group,'and

CARBAZOL CO each of R, and R (the same or different) represents hy- This invention relates to recording and reproduction drogen, an aliphatic group including a cycloaliphatic of information-wise modulated electromagnetic radia- 5 group or said groups in substituted form, e.g. an alkyl tion and to recording materials suitable therefor, and group including asubstituted alkyl group e.g. methyl or particularly relates to such processes and recording benzyl, or an aryl group e.g. phenyl, or R and R tomaterials containing one or more organic photocongether represent the necessary atoms to close a nitroductive compounds as hereinafter described. gen containing ring including such ring in substituted It has now been found that a particularly photosensi- St t tive photoconductive recording member can be formed Preferred compounds according to the present invenby using in its compositionaphotosensitive compound tion that are particularly suited for use in electrocorresponding to the following general formula! graphic recording materials are those wherein the atoms represented by 2 and Z form a carbazole nu- & I I cleus having on the nitrogen atom of the carbazole ring \L I N t a phenyl group that is substituted in the p-position with I the Ar l R 1 R1 2 wherein each of Z and Z (the same or different) represents the group as defined. necessary atoms to close an adjacent ring or ring sys- The preparation of compounds used according to the tem including such ring or ring system in substituted present invention is illustrated by the following reacform, preferably an aromatic ring e.g. benzene ring intion scheme:

/ I KOH reduction optional introduction of allgyl I or aryl groups l N N NH N\ cluding a substituted aromatic ring e.g. a halogen- Suitable photoconductive compounds falling within substituted benzene ring, the substituents being e.g. the scope of the general formula are listed in the folchlorine, bromine or iodine, lowing table I.

Table 1 Nov Formula melting point I separated as oily product Table l-Continued No. Formula melting point N N(CH2 )2 HN-CH Q w m N N HN(CHz)2-NH 6 wow Preparation of compound 1 of table I 400 g of nitrobenzene were brought into reaction with 75 g of pulverized potassium hydroxide. The temperature of the reaction mixture was adjusted to 80C with stirring. Then 100 g of carbazole were added portion wise in such a way that the temperature of the mixture continuously remained below 100C.

After addition of the complete carbazole amount the mixture was kept for 30 min at 100C. The whole was cooled overnight in a refrigerator. The residue was sucked off and washed with petroleum ether. The dried product was put into water and neutralized with acetic acid. The product obtained was sucked off and recrystallized from acetic acid or dichloroethane. A yellow product corresponding to the following formula was obtained. Melting point 211C. Yield 50%.

A mixture of 39 g of N-(p-nitrobenzene)-carbazole and 3 ml of Raney nickel was brought to a volume of 240 ml with ethylene glycol monomethyl ether. Hydrogenation was performed at 1500 psi and 80C. After 12 hours of shaking about 98% of the hydrogen had entered into reaction. The Raney nickel was filtered off, the solvent was evaporated and the residue was an oily product that slowly solidified.

Preparation of compound 2 of table 1 A mixture of 0.02 mole of compound 1 of Table I, 0.05 mole of benzyl chloride, and 0.04 mole of pulverized anhydrous sodium carbonate in anhydrous ethanol was refluxed for 27 hours. The residue was sucked off, washed first with ethanol and afterwards with water to reach pH 7. Subsequently it was recrystallized from ethylene glycol monomethyl ether. A white product was obtained.

Melting point 184C. Yield 74%. Preparation of compound 3 of Table l A mixture of 0.02 mole of compound 1 of table 1, 0.05 mole of benzyl chloride and 0.04 mole of pulverized anhydrous sodium carbonate was refluxed for 27 hours in anhydrous methanol. The residue was sucked off and consisted of compound 2. The mother lye standing for some days in a refrigerator yielded a second residue which upon recrystallization from ethyl alcohol yielded the compound 3 of Table I being a white product having a melting point of 129C.

Preparation of compound 4 of table I 0.02 mole of compound 1 to table 1 was allowed to react with 0.066 mole of pulverized anhydrous potassium carbonate and 0.16 mole of trimethyl phosphate for 48 hours at 80C. The whole was poured in a mixture of concentrated ammonium hydroxide and ice and stirred for 1 hour at ambient temperature. The product was sucked off, washed again with water to reach pH 7 and dried. Then it was crystallized from ethylene glycol monomethyl ether. A white product was obtained. Melting point 212C.

Yield 50%. Preparation of compound 5 of table 1 0.075 mole of compound 1 of table'l was allowed to react for 16 hours on an oil-bath at 100C with 0.05 mole of 1,2-dibromoethane and 0.1 g of triisopropanolamine. The residue was dissolved in 250 ml of chloroform and then boiled.

250 ml of 2N hydrochloric acid were added and the resulting mixture was shaken. A white product precipitated, which was filtrated.

'Melting point 200-220C.

By addition of 1N sodium hydroxide and after extraction with chloroform the hydrochloride was set free again. The extract was concentrated by evaporation of the volatile substances and thereafter it was boiled up with n-butanol.

The product was dissolved in hot dimethylformamide whereupon the same amount of methanol was added. Crystallization successively from dichloroethane and p-xylene with active carbon gave a white product melting at 231C.

Preparation of compound 6 of Table 1 A mixture of 0.1 mole of compound 1 ofTable 1,0.05 mole of p-xylene dichloride and 0.1 mole of triisopropanolamine was heated gently on an oil-bath; the reaction went on suddenly at C and the reaction mixture became solid. The temperature was increased to 125C and afterwards the mixture was cooled. The pale hard mass was pulverized in a mortar with 2N hydrochloric acid, sucked off and washed with water until a neutral pH value was attained. Thereafter it was sucked off, washed with methanol and ether and recrystallized from ethylene glycol monomethyl ether. A white product was obtained.

Melting point between and 123C. Yield 50 The photoconductive compounds applied according to the present invention may be used alone or in combination with substances imparting desired chemical or physical properties to the recording element. So, these substances can be combined with other substances that either or not are photoconductive and exert an influence e.g. on the dark resistivity, the dischargeability or conductivity of the recording layer by an exposure to electromagnetic radiation, or on the transparency or the quality of the final image, e.g. by counteracting the fringe effect as described in the United Kingdom Patent Specification 1,007,349 filed December 12, 1961.

g A proper combination with selected binding agents and/0r chemical sensitizing agents may result in an enhancement of the total sensitivity. The recording elements according to the present invention preferably contain at least 5 by weight of a photoconductive compound being within the scope of the above general formula. For use in electrophotography the recording element preferably consists for at least 10 72 by weight of one or more of the said compounds. The electrically insulating binding agent used in a recording layer containing said photoconductive compound(s) may provide the desired mechanical strength e.g. to form a selfsupporting layer, and preferably has a resistivity of at least 10 ohm. cm.

According to a particular embodiment the recording layer consists of the photoconductor, which, e.g., has been applied to a suitable support in molten state forming a micro-crystalline or glass-like layer on cooling. This technique can be applied when the photoconductive recording element has not topossess a high mechanical strength. For such technique reference is made to the Canadian Patent Specification 712,541 filed Feb. 5, 1960 by Gevaert Photo-Producten N.V.

Macromolecular compounds suitable for use as insu-,

lating binding agent for the photo-conductive compounds are, e.g., natural resins such as dammar resin, gum arabic, microcrystalline waxes,.modified natural substances such as cellulose diacetate, cellulose triacetate, and ethylcellulose, pentaerythrite polyesters or modified colophony resins and ester gums, polymers such as polyethylene, polystyrene and copolymers of styrene, polyvinyl acetate and copolymers of vinyl acetate, polyvinyl acetals of formaldehyde, acetaldehyede or butyraldehyde, polyacrylic acid esters and polymethacrylic acid esters, coumarine-indene resins,

epoxy resins and polycondensates such as glycerol phthalate resins and other glyceryl polyesters, alkyd resins, diethylene glycol polyesters, formaldehyde resins and silicone resins.

Preferred binding agents are halogen-containing polymers. The sensitization of organic photoconductors with halogen-containing polymers is described in the United Kingdom Patent Specification 964,878 filed May 3, l960 by Gevaert Photo-Producten N.V. Ac-

cording to said specification a material suitable for use in electrophotography comprises a photoconductive layer incorporating an organic monomeric photoconductor and a halogen-containing polymer in such layer or in a juxtaposed layer (if any), the sensitivity of said photoconductor having been increased by making it to interact with said halogen containing polymer by heatmg.

In the following table ll a list of preferred polymeric binding agents is given, which may be used in combination with the heterocyclic organic photoconductors of use according to the present invention as well as the corresponding suitable solvents.

Table II Polymeric binding agent defined by its Solvent structural unit(s) chl, o-@ C-@ 0 o,s- -so, methylene l chloride e Cl (fl cll-l, cl ---o @-c- -ooc-(cll, co methylene l chloride Cl CH3 Cl i on, o c-@-o- 0c-@-co (Fl cll Cl I methylene o o chloride I I Cl CH; C]

{ e)e-- z)s methylene chloride $H: o @O-@OOC-CHCl-CHCl-CO methylene chloride CH3 h l- C a o,s I -so,-o--c o methylene chloride CH3 t.

E -O S- SO --O-CO methylene I chloride CH3 methylene -O- chloride Table II -Continued Polymeric binding agent defined by its Solvent structural unit(s) Hg-CH methylene I chloride methylene chloride methylene chloride 9* CH, methylene chloride 10 :4 w

{CH;-CH-CHg'-CH methylene l l chloride 0 O \(':H CH,

cu F q "H c 1 th I me y ene l L chloride 10 by 80 by weight V 7 weight chloride/acec| ococl-la tone 1 :1

9l by 3 by weight weight Hg--CH CH -CH methylene i (I) chloride/ l Cl O=C acetone (1:1) I (F0 0 s5 by 14 by weight weight Table [I -Continued Polymeric binding agent defined by its structural unit(s) Solvent HQF Q CHO \CH methylene chloride/ acetone/ ethanol The inherent spectral sensitivity of most of the photoconductive compounds listed in Table I is mainly situated in the near U.V. range, ie in the range of 360 to 420 nm.

So, according to a special embodiment of the present invention semi-transparent recording layers are prepared, in which said photoconductive compounds are used in admixture with (an) inorganic photoconductive substance(s), especially photoconductive substances of the group of zinc oxide, photoconductive lead(ll) oxide and photoconductive cadmium sulphide or cadmium selenide.

Suitable spectral sensitizing dyestuffs for the organic photoconductor are among others organic dyestuffs, known as methine dyes, or xanthene dyes of which the phthaleins and rhodamines are subclasses, and triarylmethane dyes e.g. crystal violet (C.I. 42,555) and the triarylmethane dyes described in published Dutch Patent Application 6704706 filed Apr. 3, 1967 by Gevaert-Agfa N.V. the term methine dyes includes monoas well as polymethine dyes which dyes are known to those skilled in the art of the spectral sensitization of light-sensitive silver halide. Preferred methine dyes are of the cationic type. As preferred xanthene dyes Rhodamine B (C.l. 45,l70), Rose Bengale (C.l. 45,440) and Fluorescein (C.I. 45,350) are mentioned. The spectral sensitizing dyes are preferably added to the recording layer composition in a proportion of 0.01 to by weight in respect of the photoconductive substance(s).

Particularly preferred methine dyes are within the scope of the following general formulae:

wherein:

A, stands for a dimethine or tetramethine group including a substituted dimethine or tetramethine group,

n stands for 1 or 2,

R stands for alkyl including substituted alkyl, an unsaturated aliphatic group e.g. allyl, aralkyl including substituted aralkyl, aryl including substituted aryl or cycloalkyl,

R stands for alkyl, aryl including substituted aryl, e.g. phenyl and phenyl substituted preferably in the pposition by alkyl, halogen and alkoxy, a 5- or 6- membered heterocycle the heteroatom of which is oxygen, sulphur, selenium or nitrogen such as 2-, 3-, or 4- pyridyl, 2-furyl, Z-thienyl, etc. including their quaternary salts,

R stands for hydrogen or has one of the meanings given for R,,

R stands for hydrogen, alkyl, alkoxy or halogen or together with R forms an alkylene bridge such as dimethylene and trimethylene,

each of R and R (the same or different) stands for hydrogen, alkyl, alkoxy or halogen or together represent,

the atoms necessary to complete a fused-on benzene nucleus,

X, represents an anion e.g. Cl, Br, I, C10 CH3SO4, 0r

but is missing when the R group contains already an anion (betaine type salt), and Z represents the atoms necessary, to complete a heterocyclic nucleus of the types used in the production of cyanine dyes e.g. such 13 (p-toly)-thiazole, 4-(p-bromophenyl)-thiazole, 4,5- dimethylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)- thiazole, 4-(m-nitrophenyl)-thiazole, those of the benzothiazole series, e.g. benzothiazole, 4- chlorobenzothiazole, S-chlorobenzothiazole, 6- chlorobenzothiazole, 7-chlorobenzothiazole, 4- methylbenzothiazole, S-methylbenzothiazole, 6- methylbenzothiazole, S-bromobenzothiazole, 6- bromobenzothiazole, 6-sulphobenzothiazole, 4- phenylbenzothiazole, S-phenylbenzothiazole, 4- methoxybenzothiazole, S-methoxybenzothiazole, 6- methoxybenzothiazole, -iodobenzothiazole, 6- iodobenzothiazole, 4-ethoxybenzothiazole, 5-

ethoxybenzothiazole,4,5,6,7-tetrahydrobenzothiazole, 5,6-dimethoxybenzothiazole, 5,6-dioxymethylenebenzothiazole, Shydroxybenzothiazole, 6- hydroxybenzothiazole, 5,o-di-methylbenzothiazole, those of the naphthothiazole series e.g. naphtho[2,l-

d]thiazole, naphtho[ l,2-d]thiazole, 5- methoxynaphtho[ l,2-d]thiazole, 5- ethoxynaphtho[1,2-d]thiazole, 3- methoxynaphtho[2, l -d]thiazole, 7-

methoxynaphtho[2, I -d]thiazole, those of the thionaph- 5-methyl-6-methoxybenzoselenazole, 5 ,6- dioxymethylenebenzoselenazole, 5- hydroxybenzoselenazole, 4,5 ,6,7-

tetrahydrobenzoselenazole, those of the naphthoselenazole series e.g. naphtholZ,l-d]-selenazole, naphtho[ I ,2-d]selenazole, those of the thiazoline series e.g. thiazoline, 4-methylthiazoline, 4-hydroxymethyl-4- methylthiazoline, 4,6-bis-hydroxymethylthiazoline, those of the oxazoline series e.g. oxazoline, those of the selenazoline series e.g. selenazoline, those of the 2- quinoline series e.g. quinoline, 3-methylquinoline, 5-

methylquinoline, 7-methylquinoline, 8- methylquinoline, -chloroquinoline, 8- chloroquinoline, fi-methoxyquinoline, 6-

ethoxyquinoline, -hydroxyquinoline, 8 -hydroxyquinoline, etc., those of the 4-quinoline series e.g. quinoline, 6-methoxyquinoline, 7-methylquinoline, 8- methylquinoline, those of the l-isoquinoline series e.g.

l-isoquinoline, 3,4-dihydroisoquinoline, those of the 3-isoquinoline series e.g. 3-isoquinoline, those of the pyrimidine series, those of the quinoxaline series, those of the quinazoline series, those of the l-phthalazine series, those of the 2-pyridine series, e.g. pyridine, 5- methylpyridine, -3-nitropyridine, those of the 3,3- dialkylindolenine series, e.g. 3,3-dimethylindolenine, 3,3,S-trimethylindolenine, 3,3,7-trimethylindolenine, etc., those of the benzimidazole series e.g. benzimidazole, 5,6-dichlorobenzimidazole, 5- chlorobenzimidazole, 5,6dibromobenzimidazole, 5- chloro-6-amino-benzimidazole, 5-chloro-6- bromobenzimidazole, S-phenylbenzimidazole, 5- fluorobenzimidazole, 5,6-difluorobenzimidazole, 5- cyanobenzimidazole, 5,6-dlcyanobenzimidazole, 5- chloro-6-cyanobenzimidazole, 5-fluoro-6- cyanobenzimidazole, 5-acetylbenzimidazole, 5-chloro- 6-flu0robenzimidazole, S-carboxybenzimidazole, 7- carboxybenzimidazole, 5-carbethoxybenzimidazole, 7-carbethoxybenzimidazole, 5- sulphamylbenzimidazole, or S-N-ethylsulphamylbenzimidazole, S-ethylsulphonylbenzimidazole and 5- trifluoromethylsulphonylbenzimidazole;

wherein A stands for a monomethine or trimethine group including a substituted monomethine or trimethine group,

each of R' -R and R" -R" the same or different) has one of the meanings given for R R X; has the same significance as X Ill.

wherein:

each of R, and R" (the same or different) has one of A the meanings given for R X has the same meaning as X A has the same meaning as A each of m and p (the same or different) stands for 1 or 2, and

each of Z and Z (the same or different) stands for the atoms necessary to complete a heterocyclic nucleus of the thiazole, benzothiazole, naphthothiazole, thionaphtheno[7,6-d1-thiazole, thiadiazole, oxazole, benzoxazole, naphthoxazole, selenazole, benzoselenazole, naphthoselenazole, Z-quinoline, 4-quinoline, pyrimidine,

quinoxazoline, Z-pyridine, 3,3-dialkylindolenine or of the benzimidazole series;

representative examples of these heterocyclic nuclei can be found above in the definition of Z in formula I. The dyestuffs corresponding to the above general formulae can be prepared according to the methods known by those skilled in the art of methine dye chemistry.

According to a further embodiment of the invention, the recording material contains one or more substances that increase the photoconductivity of the recording material in the inherent spectral sensitivity range of the said heterocyclic organic photoconductive compounds. As already has been said a binding agent can act as a sensitizing agent that enhances the total sensitivity of the recording element. In this respect compounds are to be mentioned which contain one or more electronattracting atoms or groups e.g. those that are known as non-ionic Lewis acids, e.g. the Lewis acids that can form a charge transfer complex as described in U.S. Pat. No. 3,408,183 of Joseph Mammino issued Oct. 29, 1968. Good sensitizing results are obtained with organic carboxylic acid anhydride compounds and with quinones containing electron-attracting substituents e.g. halogen or cyano, such as in tetrachlorobenzoquinone, tetracyanobenzoquinone and in organic compounds containing group, and with the compounds according to the structural formula of the Belgian Patent Specification 734,141 filed June 6, 1969 by Gevaert-Agfa N.V. and the chlorineand/or cyano-containing polymers of Table 11.

The photoconductive compounds may be used in admixture with diazonium salts that on exposure to electromagnetic radiation produce (a) radical(s) that irreversibly increase(s) the electro-conductivity of a recording layer. Such substances as well as details about their incorporation into a recording layer containing an organic photoconductive insulating substance are described in the United Kingdom Patent Specification 964,872 filed Apr. 22, 1959 by Gevaert Photo- Producten NV. and the U.S. Pat. No. 3,113,022 of Paul Maria Cassiers, Jean Marie Nys, Jozef Frans Willems and Rene Maurice Hart issued Dec. 3, 1963. A particularly suitable conductivity-increasing diazonium compound is p-nitrobenzenediazonium chloride. The diazonium compounds are preferably used in an amount of 0.01 to 10 by weight in respect of the present photoconductive heterocyclic organic compounds.

Other additives well known in the art of preparing photoconductive coatings for recording purposes may be used, eg matting agents, fluorescing compounds, phosphors, optical brightening agents, agents controlling the adhesive power of the recording layer, agents controlling the elasticity, the plasticity and the hardness of the recording layer, agents controlling the viscosity of the coating composition, antioxidants, glossimproving agents, etc.

Transparent and semi-transparent recording materials containing the photoconductive heterocyclic organic compounds are described hereinbefore are especially suited for use in recording materials applied for the production and reproduction of microfilm images. Microfilm images can be copied in contact or enlarged optically on recording materials according to the pres ent invention. According to the type of development, the transparencies obtained (contact copies and enlargements) can serve as negative or positive intermediate prints for further printing, e.g. on diazotype materials.

The semitransparent recording materials according to the present invention preferably have an optical density not larger than 0.30 towards visible light or the copying light used in the printing apparatus wherein it is used as intermediate print.

The photoconductive heterocyclic organic compounds described hereinbefore are further especially suited for use in the production of pigment images wherein the latter may have the properties of a fluorescent compound or phosphor. As is generally known luminescent phosphors are used in screens of cathoderay tubes and more particularly in television, X-ray, radar and oscilloscope screens.

ln colour television screens phosphors of different colour have to be fixed on a screen in a particular pattern.

The described photoconductive compounds are used successfully in a process for the production of colour television screens as described in the French Patent Specification 1,336,499 filed Sept. 26, 1962 by Comp.- Francaise Thomson-Houston. According to the process described in said specification a pattern of a phosphor on a screen support is produced by the steps of applying to said support a coating of an electroconductive material and to said coating a layer comprising a vaporisable or thermolysable photoconductive compound optionally incorporated in a vaporisable or thermolysable binding agent. On said coating an electrostatic charge pattern corresponding with the pigment pattern to be produced is formed in an electrophotopgrahic way, and the electrostatic charge pattern is developed with non-volatile powder particles that have the desired phosphorescent or luminescent properties. Subsequently, the photoconductive layer containing the phosphor powder image is heated to remove the volatile substances of the photoconductive recording layer and to make the phosphor pattern adhere to the screen support.

In order to fix the powder image before applying the heating step it is preferably overcoated with a layer of a thermolysable binding agent.

According to said French Patent Specification photoconductors of the group of anthracene, anthraquinone and xanthene are used. The recording layer may further contain boric acid.

The photoconductors mentioned in the French Patent Specification are advantageously substituted partly or wholly by the photoconductive substances applied according to the present invention.

Suitable thermolysable binding agents belong to the class of the polyacrylic acid esters and polymethacrylic acid esters, e.g. polymethyl methacrylate, polyethyl methacrylate and polyethyl acrylate.

The thickness of the photoconductive layers of the present invention is not critical but is open to choice within a wide range according to requirements in each individual case. Good results are attained with photoconductive layers of a thickness between 1 and 30 p. preferably between 2 and 20 t. Too thin layers do not have a sufficient insulation power in the absence of active electromagnetic radiation, whereas too thick layers require extensive exposure times.

In the manufacture of electrophotographic recording materials according to the present invention a relatively conductive support for the recording layer is used, e.g. an electroconductive sheet or plate, or an insulating sheet or plate covered with an electroconductive interlayer. BY electro-conductive plate or sheet is understood a plate or sheet whose electrical resistivity is smaller than that of the non-irradiated (darkadapted) photoconductive layer i.e. in general smaller than ohm.cm and preferably is at least 100 times as small as that of the recording layer. Supports whose resistivity is not higher than 10 ohm.cm are preferred. The recording layers themselves preferably have an electrical insulating power as high as possible without affecting too much the photosensitivity by means of too high an amount of insulating binding agent. In nonirradiated state (dark-adapted state) the recording layers preferably have a resistivity of at least 10 ohm. cm.

Suitable conductive plates are, e.g. plates of metals such as aluminium, zinc, copper, tin, iron, or lead.

Suitable electro-conductive interlayers for insulating supports are, e.g. vacuum-coated metal and conductive metal compound (metal oxide or metal salt) layers such as silver, tin, aluminum, and copper iodide conductive layers, transparent conductive polymer layers, e.g. applied from polymers containing quaternized nitrogen atoms, such as those described in the United Kingdom Patent Specification 950,960 filed Sept. 23, 1960 by Gevaert Photo-Producten N.V., or layers containing conductive particles, e.g. carbon black and metal particles dispersed in a binder. The binder used for said particles has a resistivity preferably lower than 10 ohm.cm. A suitable binder for that purpose is gelatin.

It is possible to produce transparent photoconductive recording materials by applying the photoconductive compounds together with a suitable binder (if necessary) from a clear solution to a conductive transparent base or a transparent insulating base coated with an electroconductive transparent interlayer.

As transparent bases resin sheets having an optical density of not more than 0.10 are preferred, e.g. a sheet made of polyethylene terephthalate or cellulose triacetate. The conductive interlayer preferably consists of a metal coating, e.g., a vacuum-coated aluminium layer having an optical density of not more than 0.30, or of a conductive transparent polymer layer composed, e.g. 'of an organic polyionic polymer, e.g. a polymer containing quaternized nitrogen atoms such as a quaternized polyethylene-imine.

In reproduction techniques wherein the prints are to be produced on an opaque background preferably a paper sheet is used as support for the recording layer.

Paper sheets that have an insufficient electrical conductivity are coated or impregnated with substances enhancing their conductivity, e.g. by means of a conductive overcoat such as a metal sheet laminated thereto.

As substances suited for enhancing the conductivity of a paper sheet and which can be applied in the paper |mass are particularly mentioned hydroscopic com pounds and antistatic agents as described, e.g. in the United Kingdom Patent Specification 964,877 filed May 2, 1960 by Gevaert Photo-Producten N.V., and antistatic agents of polyionic type, e.g. CALGON CONDUCTIVE POLYMER 261 (trade mark of Calgon Corporation, Inc. Pittsburgh, Pa., U.S.A.) for a solution containing 39.1% by weight of active conductive solids, which contain a conductive polymer having recurring units of the following type:

Paper sheets are preferably impermeabilized to organic solvents, e.g. by means of a water-soluble colloid or by strongly hydrating the cellulose fibers such as in the case of glassine paper.

In order to prepare an electrophotographic material according to the present invention various techniques may be applied.

In practice, the photoconductive substances involved, either alone or together with other additives such as those described above, preferably are first dissolved or dispersed in a suitable organic solvent such as a chlorinated hydrocarbon, e.g. methylene chloride. The solution or dispersion thus obtained is spread uniformly on a surface of a suitable support, e.g. by centrifuging, spraying, brushing, or coating. Thereupon the layer formed is dried in such a way that a solid photo conductive layers is formed on the surface of the support.

Recording materials according to the present invention can be used in any of the different techniques known in recording with the aid of photoconductors. According to a preferred embodiment they are used in a technique based on the discharge of an electrostatically charged recording layer by exposure to light.

Photoconductive recording materials prepared according to the present invention can be used in exposure units equipped with incandescent lamps, so that they need not be exposed to light rays rich in ultraviolet such as those emitted by a high-pressure mercury vapour bulb.

The electrostatic charging of photoconductive recording elements according to the present invention can be effected according to any method known in electrophotography, e.g. by friction with a smooth material, with a material possessing a high electric resistance, e.g. a cylinder coated with polystyrene, by corona discharge, by contact charge, or by discharge of a capacitor.

Recording materials containing the said organic photoconductive substances can be used in a recording technique comprising a negative corona charging as well as in a recording technique comprising a positive corona charging.

For the production of an electrostatic image it is possible to effect the charging and exposure steps simultaneously and even to expose the recording layer imagewise before the charging since a conductivity image is formed that is not destroyed immediately, especially when diazonium salts are used in the recording element. It is preferred, however, to performthe charging before the image-wise exposure.

The electrostatic latent image can be converted into a visible image either on the electrophotographic material wherein the latent image was formed, or on a material to which the electrostatic latent image was transferred, e.g. by application of the method described in the Belgian Patent Specification 529,234 filed May 29, 1954 by Chester Floyd Carlson.

The conversion of the original or transferred latent image into a visible image can occur according to one of the techniques known in electrophotography, wherein use is made of a conductivity pattern (e.g. electrolysis) or the electrostatic attraction or repulsion of finely divided coloured substances, which, e.g. are present in a powder mixture, in an electrically insulating liquid (e.g. in the form of a suspension) or in a gas (e.g. in the form of an aerosol), or wherein electrostatic attraction is used for selectively wetting charged portions of the recording layer, as described in the United Kingdom Patent Specifications 1,020,505 filed Nov. 8, 1961 and 1,033,419 filed Nov. 26, 1962 both by Gevaert Photo-Production N.V.

When the sign of the charge of the developing powder or developing liquid is properly chosen, either a negative or a positive print can be obtained from any original. If both printing material and developing powder or developing liquid have the same sign of charge, the powder only adheres to the discharged areas so that a negative print is obtained. If the signs of the recording material and of the developing powder or developing liquid differ, a positive print is obtained.

If a coloured popwder is used for making visible the latent image, the visible image obtained can, if necessary, be fixed according to one of the methods known in electrophotography, e.g. by heating, or it can be transferred to another support, e.g. according to the method described in the United Kingdom Patent Specification 658,699 filed Apr. 14,1949 by Battelle Memorial Institute and fixed thereon.

The present heterocyclic organic photoconductive compounds can also be supplied in a thermoplastic recording process to form a ripple-image as described, e.g. in the United Kingdom Patent Specification 964,881 filed May 17, 1960 by Gevaert Photo- Producten N.V.

Evidently, the present invention is by no means limited to one or other particular embodiment of using the electrophotographic material containing the photoconductive compounds as described herein. The exposure technique, the charging method, the formation of the charge pattern, the transfer of such pattern if applied, the developing method, and the fixation or the transfer of the developing material pattern may be modified or adapted.

The composition of the recording materials used in these methods may be adapted to the requirements of the recording process used.

Electrophotographic materials according to the present invention can be employed in reproduction techniques, wherein different kinds of electromagnetic radiations are used, e.g. visible light, U.V.-radiation, X- rays and y-rays.

The present invention is illustrated by the following examples.

The percentages and ratios are by weight unless otherwise indicated.

EXAMPLE 1 An aluminium-laminated paper sheet was coated with the following composition:

10% by weight solution in methylene chloride of an organic photoconductor listed in The coating was carried out in such a ratio that the dried photoconductive layer contained 2 g of photoconductor per sq.m.

After a negative corona charging with a potential difference of -6000 V between the corona wires and the ground, the charged recording layer was contactexposed for 30 see. through a step wedge having 0.20 log exposure increments. in this exposure 5 05mm (trade name) L 20 fluorescent tubes, mainly emitting in the UV. range and the shorter wavelengths of the visible spectrum were placed at a distance of 20 cm from the recording layer.

The latent wedge image obtained was electrophoretically developed by means of an electrophoretic developer prepared by diluting the concentrated developer composition described hereinafter in a volume ratio of 15/1000 by means of ISOPAR H (an isoparaffinic hydrocarbon mixture having a boiling range of 177-188C sold by Esso Belgium N.V., Antwerp, Belgium):

carbon black (average particle size 20 nm) 30 g zinc monotridecyl phosphate as dispersing agent 1.5 g

ISOPAR H (trade name) 750 ml resin solution prepared as described hereinafter 150 g.

The resin binder solution was prepared by heating 500 g of ALKYDAL L 67 (a trade name of Farbenfabriken Bayer A.G., Leverkusen, W. Germany for a linseed oil-modified (67 by weight) alkyd resin) and 500 m1 of white spirit containing 1 1 by weight of aromatic compounds at 60C till a clear solution was obtained, and subsequent cooling.

A black positive copy of the wedge original on a transparent base was obtained.

From the wedge prints obtained the relative speed values of the developed materials were calculated based on a comparison of the number of non-toned (discharged) steps present in the wedge prints obtained with materials containing a photoconductor of Table 1 with the number of non-toned steps produced in a material containing photoconductor number 2 of Table Ii to which is given arbitrarily the speed value 100.

Number of compound of Table 1 Relative Speed values EXAMPLE 2 An electrophotographic recording material was prepared by coating onto an aluminium-laminated paper a solution containing:

The dried recording layer contained 2 g of photoconductor per sq.m.

The coated samples were negatively charged with a negative corona having a potential difference of 6000 V between the corona wires and the ground.

The charged recording layer was contact-exposed for 6 sec. through a step-wedge having 0.20 log exposure increments. in the exposure tungsten filament light was used.

The latent wedge images were electrophortetically developed as described in Example 1.

The relative speed values of the developed materials were compared with those of the electrophotographic material containing photoconductor number 6 of Table l which is given arbitrarily the speed value 100.

Number of compound of Table l Relative speed values EXAMPLE 3 To a polyethylene terephthalate support of 100 u a conductive transparent coating was applied from an aqueous solution of gelatin and CALGON CONDUC- TlVE POLYMER 26] (trade mark) in a weight ratio of 2:1. Coating was carried out in such a way that the dried coating contained 2 g of gelatin per sq.m. The electrical surface resistance of the coating was 1 X 10 ohm per sq.cm measured at a relative humidity of 50 50 An electrophotographic recording material was prepared by coating onto said conductive layer a solution consisting of -Continued Rhodamine B (C.l. Basic Violet 10;

Cl. 45.l70) 0.025 g.

The dried recording layer containing approximately 3 g of photoconductor per sq.m was charged with a negative corona and contact-exposed with 500 lux.sec with the same light source as in Example 2. The latent image was electrophoretically developed for 5 sec with the developer described in Example 1. A good copy of the original was obtained.

EXAMPLE 4 To a polyethylene terephthalate support of 63 u a conductive transparent coating was applied from :1 I07: aqueous solution of polystyrene sulphonic acid sodium salt methanol 40 ml 60 ml.

compound 6 of Table l 5 g methylene chloride 45 g l,2-dichloroethane 45 g PARLON P-20 (marketed by the Hercules Powder Company, Inc., Wilmington, Del. USA) chlorinated polypropylene 66.89% of chlorine 5 g.

After a negative corona charging with a potential difference of 6000 V the charged recording layer was contact-exposed for 2 see through a positive transparency of a test chart with 8 Osram (trade name) L 20 fluorescent tubes at a distance of 20 cm from the recording layer.

After the exposure the latent image was developed for 5 sec with a triboelectrically charged positive toner on the base of three parts by weight of pitch, 4 parts by weight of colophony and 3 parts by weight of carbon black.

A contrasty transparent positive copy of the transparency was obtained.

EXAMPLE 5 The effect on the speed of electrophotographic recording materials resulting from a few chemical sensitizers was examined.

Therefore the following photoconductive compositions were coated on an aluminium-laminated paper:

10% by weight solution in methylene chloride of the organic photoconductor nr. 2 of Table l ml copoly(vinyl chloride/vinyl acetate/maleic anhydride)(molar ratio 86.5/l3.3/0.2) 5 g a chemical sensitizer listed in Table III below 0.05 g.

Table III EXAMPLE 6 Test E i f t relllivi Electrophotographic recording materials were pre- 6 Spec pared-by coating onto a conductive layer as described none 100 in Example 3 a composition containing: 1 I-II 250 l L compound 6 of Table I 5 g copoly(vinyl chloride/vinyl acetate/maleic 2 Cl anhydride)(MoIar ratio 86.5/l3.3/0.2) 5 g I methylene chloride 45 ml C l.2-dichloroethane 45 ml a sensitizing dye as listed in tabel IV 0.025 g HQC C-Cl 400 l 1 Cl-C=-=CCl 3 0 fl 600 The recording layers were charged, exposed and developed as described in Example 3. From the obtained prints the relative speed values H were calculated based on a comparison of the speco trally sensitized materials with the material without 4 1 NH 400 spectral sensitizer to which arbitrarily the speed value of 100 was given. N0

The relative speed values are listed hereinafter.

Table IV No. Structural formula of spectral Relative sensitizing agent speed value 0 none HOOC- 250 c Cl H C C H /N =N\ H C 0 C2H5 1ICH=C I l i I Br 300 l C H C H 3 a CH N 250 ll I CCH=CH-C l C CH3 4 S CH=CHC C I-I 25 26 We claim: 3. A recording process according to claim 1, wherein l. A recording process comprising producing by ex- R, and R represent a methyl or benzyl group. posure to imagewise modulated electromagnetic radia- 4. A recording process according to claim 1, wherein t1on a pattern of increased conductivity in a photoconthe photoconductive compound corresponds to the folductive insulating recording element comprising an or- 5 lowing general formula: ganic photoconductive compound corresponding to the following general formula:

f '3 qllo rlll r" l I N I l Ar r 'I h T A- NH N I wherein: k, Z and Z have the same significance as in claim 1,

A represents an alkylene group or an alkylene chain inwherein: terrupted by a phenylene group, and each of Z, and Z (the same or different) represents the Ar r pr n s a phenylene group. necessary atoms to close a benzene nucleus, 5. A method as in claim 1 comprising the steps of Ar represents a phenylene group, producing an electrostatic charge pattern by electroeach of R and R (the same or different) represents hystatically charging and information-wise exposing to drogen, an alkyl group, a cycloalkyl group, or a benzyl electromagnetic radiation said recording element progroup. 2 ducing thereby an information wise increase of the con- 2. A recording material containing a photoconducductivity in the recording element, and developing the tive insulating recording layer capable of being charged resulting latent electrostatic charge pattern with an electrostatically in the absence of active electromageleer ostatically ultractable substance. netic radiation and of retaining the applied charge for 6 A pr es according to claim 1, wherein the rea period of time sufficiently long to produce thereon a cording element is a recording layer that has been apdeveloped electrostatic charge pattern, characterized li d to a conductive layer or support h i a resistivin that the recording layer stands in electroconductive 1 lower h h of h da kqldapted recording l relationship to a layer or support with lower resistivity ment and Contains an Organic Photoconductive compound 7. A process according to claim 6, wherein the concorresponding to the following general formula: ductivity layer or support has a resistivity at least 10 as low as that of the recording element in the dark.

8. A recording material according to claim 2,

I wherein the photoconductive compound corresponds I i to the following general formula:

Ar 4 I 2' z 'z 9 I 2 l \12 I N J, I N a,

Al' .lll' HN-A-NH wherein: each of Z and Z (the same or different) represents the wherein necessary atoms to close a benzFne nucleus Z and Z have the same significance as in claim 2, each of R1 and R2 (the Same or d'fferem) represents A represents an alkylene group or an alkylene chain indrogen, an alkyl group, a cycloalkyl group, or a benzyl terrupted by a phenylene group, and group and Ar represents a phenylene group. Ar represents a phenylene group.

UNITED STATES PATENT AND TRADEMARK OFFICE EBTIFICATE OF CORRECTION PATENTNO. ,509

DATED October 14, 1975 INVENTOHS): Wilhelmus Janssens et a1 fiwcmmmdmmmmrwmmsmmewwe4mmfimdmmmamtmtwmLdmmPmmt mehmflwcmmcwdas wwnbdow In the Claims:

Column 26, line 27 "ultractable" should read attractable Signed and Sealed this thirteenth Day of April1976 [SEAL] A tles I:

RUTH C. MASON C. MARSHALL DANN Alltslillg Officer Commissioner 01' Pate/'11s and Trademarks 

1. A RECORDING PROCESS COMPRISING PRODUCING BY EXPOSURE TO IMAGEWISE MODULATED ELECTROMAGNETIC RADIATION A PATTERN OF INCREASED CONDUCTIVITY IN A PHOTOCONDUCTIVE INSULATING RECORDING ELEMENT COMPRISING AN ORGANIC PHOTOCONDUCTIVE COMPOUND CORRESPONDING TO THE FOLLOWING GENERAL FORMULA:
 2. A recording material containing a photoconductive insulating recording layer capable of being charged electrostatically in the absence of active electromagnetic radiation and of retaining the applied charge for a period of time sufficiently long to produce thereon a developed electrostatic charge pattern, characterized in that the recording layer stands in electroconductive relationship to a layer or support with lower resistivity and contains an organic photoconductive compound corresponding to the following general formula:
 3. A recording process according to claim 1, wherein R1 and R2 represent a methyl or benzyl group.
 4. A recording process according to claim 1, wherein the photoconductive compound corresponds to the following general formula:
 5. A method as in claim 1 comprising the steps of producing an electrostatic charge pattern by electrostatically charging and information-wise exposing to electromagnetic radiation said recording element producing thereby an information wise increase of the conductivity in the recording element, and developing the resulting latent electrostatic charge pattern with an electrostatically ultractable substance.
 6. A process according to claim 1, wherein the recording element is a recording layer that has been applied to a conductive layer or support having a resistivity lower than that of the dark-adapted recording element.
 7. A process according to claim 6, wherein the conductivity layer or support has a resistivity at least 102 as low as that of the recording element in the dark.
 8. A recording material according to claim 2, wherein the photoconductive compound corresponds to the following general formula: 